Class 11 Physics · Chapter 7 · Test 3
Diffraction, Beats, Doppler Effect
53 MCQs This test covers diffraction of waves and the ripple tank, beats and tuning of instruments, and wave intensity (I = P/A, I ∝ A²) with numericals. It also covers the Doppler effect for a moving source, with RADAR, SONAR, red and blue shift, the radar trap and medical applications.
53 questions · 45 min · 53 marks
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Sample questions
The first 5 of 53. Try each one, then tap to see the answer.
Question 1
Diffraction of waves is the:
- ABending of waves around sharp edges of obstacles or through openings
- BReflection of waves from a surface
- CChange of speed of waves on entering a new medium
- DAddition of two waves in phase
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Answer: A
Diffraction is the spreading or bending of waves around the edges of obstacles or after passing through an opening.
Question 2
Diffraction is most significant when the size of the obstacle or gap is:
- AMuch larger than the wavelength
- BComparable to the wavelength
- CInfinitely large
- DZero
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Answer: B
Diffraction occurs noticeably when the obstacle or gap is comparable in size to the wavelength.
Question 3
The narrower the gap compared with the wavelength the:
- ALess the waves spread
- BGreater the reflection
- CGreater the spreading of the waves
- DSmaller the frequency
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Answer: C
A narrower gap relative to the wavelength produces greater spreading.
Question 4
Which of the following is an example of diffraction?
- AEcho from a cliff
- BRainbow formation
- CShadow of a tree
- DHearing sound around a corner
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Answer: D
Sound bends around corners because its wavelength is comparable to everyday obstacles.
Question 5
X-rays are diffracted by crystals because the spacing between atoms is:
- AComparable to the X-ray wavelength
- BMuch larger than the X-ray wavelength
- CMuch smaller than the X-ray wavelength
- DZero
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Answer: A
Diffraction needs a spacing comparable to the wavelength and atomic spacing is of the order of the X-ray wavelength.
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